Blockchain

Blockchain
	File:Blockchain structure.svg
	A conceptual diagram of blocks linked in sequence, each containing a cryptographic hash of the previous block
Type	Distributed ledger technology, Peer-to-peer network, Cryptographic protocol
Related	Bitcoin, Cryptocurrency, Distributed computing, Peer-to-peer network, Smart contract
Inspired by	Hash chain, Merkle tree, Public key cryptography
Wikidata	Q20514253

Blockchain is a distributed, append-only database that records information in a series of cryptographically linked blocks. It is designed to provide a secure, tamper-resistant, and verifiable record of transactions or other data without requiring a trusted central authority.

Overview

A blockchain consists of a chain of data blocks, each containing a set of records (often called transactions), a timestamp, and a cryptographic hash of the previous block. This structure creates a secure and verifiable history, as altering any block would require modifying all subsequent blocks and gaining control of the majority of the network's verification power.

Blockchains are typically maintained by a peer-to-peer network of nodes that use a consensus algorithm to agree on the validity of new blocks. Once a block is accepted by the network, it becomes part of the permanent record.

Key Concepts

Distributed ledger: The database is replicated across many independent nodes, reducing the risk of single points of failure.
Cryptographic hashing: Ensures data integrity by creating unique digital fingerprints of block contents.
Consensus mechanism: A protocol (such as Proof of Work or Proof of Stake) by which nodes agree on the state of the ledger.
Immutability: Once confirmed, records are practically irreversible without redoing the work or control over the network majority.
Transparency: Public blockchains are readable by anyone, though data may be pseudonymous.

Types of Blockchain

Public blockchain: Open to anyone to read or participate in verification (e.g., Bitcoin, Ethereum).
Private blockchain: Restricted participation, often within organizations.
Consortium blockchain: Controlled by a group of pre-selected nodes or organizations.

Applications

Although originally developed for digital currencies such as Bitcoin, blockchain technology has been adapted for:

Decentralized finance (DeFi)
Supply chain tracking
Digital identity management
Secure voting systems
Intellectual property tracking
Distributed computing and storage

Limitations

Scalability: Many blockchain systems face performance bottlenecks compared to centralized databases.
Energy consumption: Proof-of-Work consensus can require significant computational resources.
Governance: Disputes or required upgrades can be difficult to coordinate in decentralized networks.
Privacy concerns: Public ledgers can reveal patterns of activity even if identities are pseudonymous.

References

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